Method for Bearer Independent Call Control (Bicc) Optimization for Ip Bearer Support

ABSTRACT

A method is disclosed for the optimization of a BICC (Bearer Independent Call Control) IP Bearer Support in a WCDMA R4 Telecommunication system, and provides for exchange of IPAddress and Port Id between two MGWs by avoiding tunneling between two MSCs, reducing the number of message exchanges, and reducing the message sizes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention in general relates to the telecommunicationtechnology. More particularly, the present invention relates tooptimization of BICC (Bearer Independent Call Control) IP Bearer Supportin a WCDMA R4 Telecommunication system.

2. Description of the Related Art

IP networks are fundamentally different from connection-orientednetworks such as those based on TDM or ATM, in that signaling messagesdo not need to be acted upon by all the network elements for User Planecommunication to take place. If the Gateways or Inter-working points canexchange information, then the IP network can route the user planepackets between the gateways. The exchange of information is simple andconsists of IP address, port numbers and some information on the type ofmedia required.

In IP networks utilizing SIP as the call control protocol, theinformation concerning the media is defined in the Session DescriptionProtocol (SDP). SDP specifies the definition of the data format and itsmeaning.

For the UMTS Core Network, ATM is used in the transport network userplane and the transport network control plane with BICC as the callcontrol protocol on the Nb interface. As BICC call control proceduresare independent of the bearer technology, these protocols can also beused over the IP networks.

IP Bearer Control Protocol (IPBCP) is suitable for use in IP networkenvironments where the Bearer Independent Call Control (BICC) isdeployed. The purpose of IPBCP is to exchange information between thetwo BIWFs. BICC IPBCP is used for the exchange of media streamcharacteristics, port numbers and IP addresses of the source and sink ofmedia stream to establish and allow the modification of IP bearers. Theexchange of information with IPBCP is done during the BICC callestablishment and after a call has been established. IPBCP uses theSession Description Protocol to encode this information.

The IPBCP makes use of the BICC Bearer Control Tunneling Protocol whichprovides a tunneling mechanism over the “horizontal” BICC interfacebetween CCUs and the “vertical” CBC interface between CCU and the BCU.

This operates as follows: (Refer FIG. 3):

Note: To explain the invention Forward Bearer Delayed TunnelingTechnique is used.

-   -   1. MSC-A (also referred to as Originating Mobile Switching        Centre from now on) initiates bearer establishment procedure by        sending BICC IAM message with BNC Characteristics set to IP/RTP        indicating IP Bearer needs to be established, codec list        indicating that codes negotiation is required, Tunneling        Indicator set to tunneling to be used and no tunnel data        indicating that bearer establishment type is Delayed tunneling.    -   2. MSC-B (also referred to as Terminating Mobile Switching        Centre from now on) after processing IAM, performs Prepare        Bearer procedure by sending AddRequest message to MGW-B (also        referred to as Terminating Media Gateway from now on).        AddRequest contains the selected codec for bearer establishment.        BNC Characteristics set to IP/RTP and tunneling option set to        delayed tunneling indicating that MGW needs to wait for IPBCTP        Request message.    -   3. MGW-B responds with AddReply message that contains the BIWF        Address and BCNId.    -   4. MSC-B indicates to MSC-A the selected codec for bearer        establishment, tunneling indicator that is set to tunneling        used, BIWF Address and the BNCId through BICC APM message.    -   5. MSC-A now performs Establish Bearer procedure by sending        AddRequest message containing the Codec type that needs to be        used for bearer establishment and the tunneling option set.    -   6. MGW-A (also referred to as Originating Media Gateway from now        on) responds with AddReply message. MSC-A waits for tunnel data.    -   7. MGW-A sends NotifyMessage with IPBCTP Request message        containing the MGW's IPAddress and PortId information.    -   8. MSC-A responds with NotifyReply confirming the receipt of        tunnel data.    -   9. MSC-A now responds to MSC-B the IPBCTP Request message as the        tunnel data through BICC APM message.    -   10. MSC-B sends a ModifyRequest message to MGW-B containing the        IPBCTP Request message as tunnel data received in the APM        message.    -   11. MGW-B responds with ModifyReply message. MSC-B waits to        receive the tunnel data.    -   12. MGW-B sends the NotifyRequest message containing the IPBCTP        Accept message with its own IPAddress and PortId as tunnel data.    -   13. MSC-B responds with NotifyReply confirming the receipt of        the tunnel data.    -   14. MSC-B sends the IPBCTP Accept message as tunnel data to        MSC-A in the APM message.    -   15. MSC-A sends ModifyRequest message to MGW-A with tunnel data.    -   16. MGW-A responds with ModifyReply. At this point in time, both        the MGWs are aware of each others IPAddress and PortId.    -   17. After RabAssignment procedures are successful on MSC-A        towards the source RNC, it sends COT message to MSC-B to        indicate that bearer establishment is successful on the        originating side.    -   18. MSC-B after successful bearer establishment on terminating        side, sends the ACM message to MSC-A.    -   19. And when terminating party answers, MSC-B sends the BICC ANM        message to MSC-A.

Sample IPBCTP Message v=0 o=−0 4727641859017609960 IN IP4 60.20.1.200s=IPBCP Message c=IN IP4 60.20.1.200 t=0 0 a=ipbcp:1 Request m=audio5098 RTP/AVP 97 a=rtpmap:97 VND.3GPP.IUFP/16000

In the above data, only IP Address (60.20.1.200 in the above exampledata) and Port Number (5098 in the above example data) fields are ofsignificance for an MGW. Since all other information is redundant, therequired information namely the IP Address and Port Id can becommunicated between MGWs through the BICC Call Control Protocol in theform of BIWF Address and BNCId fields provided by BICC.

All other fields are either unused or have predefined values which arenot interpreted by the MGW receiving the IPBCP message.

Sample APM Message Carrying IPBCTP Data APM -->1f 00 00 00 41 01 78 bb85 81 c0 00 00 01 82 81 02 07 82 81 04 08 2b 81 81 22 20 20 76 3d 30 0a6f 3d 2d 20 30 20 34 30 36 36 31 31 33 38 34 36 32 38 33 31 31 32 38 3638 20 49 4e 20 49 50 34 20 36 30 2e 32 30 2e 31 2e 32 30 30 0a 73 3d 4950 42 43 50 20 4d 65 73 73 61 67 65 0a 63 3d 49 4e 20 49 50 34 20 36 302e 32 30 2e 31 2e 32 30 30 0a 74 3d 30 20 30 0a 61 3d 69 70 62 63 70 3a31 20 52 65 71 75 65 73 74 0a 6d 3d 61 75 64 69 6f 20 35 30 38 32 20 5254 50 2f 41 56 50 20 39 37 0a 61 3d 72 74 70 6d 61 70 3a 39 37 20 56 4e44 2e 33 47 50 50 2e 49 55 46 50 2f 31 36 30 30 30 0a 22 00

In the above APM data, the highlighted portions indicate an IPBCTPrequest being tunneled though BICC.

The following are the problems in the existing system:

-   -   1. Large and Redundant messages (Extra H.248.1 Notifies and        Modifies) exchanged over Mc and Nc Interfaces thereby increasing        the processing time at MGW in terms of encoding and decoding of        these messages.    -   2. Delayed Call Setup.    -   3. Support for IPBCTP in MSC Server and IPBCP in MGW in order to        support IP Bearer.

SUMMARY OF THE INVENTION

The invention deals with optimization of BICC procedures for IP Bearersupport. The invented method is to provide for exchange of IPAddress andPort Id between two MGWs by:

-   -   1. Avoiding tunneling between two MSCs.    -   2. Reducing the number of message exchanges.    -   3. Reducing the message sizes.

UMTS Core Networks employ ATM in transport network user plane andtransport network control plane with BICC as the call control protocolon the Nb interface. As BICC call control procedures are independent ofthe bearer technology, BICC can be used over the IP networks.

IP Bearer Control Protocol (IPBCP) is used over IP network environmentswhere BICC is deployed. BICC IPBCP is used for exchange of media streamcharacteristics, port numbers and IP addresses of the source and sink ofmedia stream to establish and allow the modification of IP bearers. Theexchange of this information with IPBCP is done during the BICC callestablishment and after a call has been established.

The current invention proposes an optimization technique for theexchange of such information over BICC protocol without necessarilyusing IPBCP.

Accordingly the present invention relates to IP Bearer Support in aWCDMA system without using IPBCTP and IPBCP protocols wherein onlyinterpretation of existing procedures is changed and not messages andparameters.

Accordingly, this invention explains a method for Bearer IndependentCall Control (BICC) optimization for IP bearer support wherein aOriginating Mobile Switching Centre initiates bearer establishmentprocedure by sending BICC IAM message with BNC characteristics set toIP/RTP indicating the need of IP Bearer establishment and codec listindicating the codec negotiation requirement.

A Terminating Mobile Switching Centre after processing IAM, performsPrepare Bearer procedure by sending AddRequest message to a TerminatingMedia Gateway where AddRequest contains the selected codec for bearerestablishment and BNC Characteristics set to IP/RTP. For the saidrequest a Terminating Media Gateway responds with AddReply message thatcontains the IPAddress which is in BIWF Address and PortId which is inBCNId. Terminating Mobile Switching Centre indicates to OriginatingMobile Switching Centre the selected codec for bearer establishment,BIWF Address and the BNCId through BICC APM message. Originating MobileSwitching Centre performs Prepare Bearer procedure by sending AddRequestmessage containing the Codec type that is used for bearer establishment,remote IPAddress and the PortId. A Originating Media Gateway respondswith AddReply with its own IPAddress and PortId. Originating MobileSwitching Centre responds to Terminating Mobile Switching Centre withOriginating Media Gateway's IPAddress and PortId through BICC APMmessage. Terminating Mobile Switching Centre sends a ModifyRequestmessage to Terminating Media Gateway containing the originating sidesIPAddress and PortId.

Terminating Media Gateway responds with ModifyReply where, both the MGWsare aware of each other's IPAddress and PortId. After RabAssignmentprocedures are successful on Originating Mobile Switching Centre towardsthe source RNC, it sends COT message to Terminating Mobile SwitchingCentre to indicate that bearer establishment is successful on theoriginating side. Terminating Mobile Switching Centre, after successfulbearer establishment on terminating side, sends the ACM message toOriginating Mobile Switching Centre. When terminating party answers,Terminating Mobile Switching Centre sends the BICC ANM message toOriginating Mobile Switching Centre. BICC for IP Bearer support performsPrepare Bearer Procedure to retrieve IPAddress and PortId from itsassociated MGW whenever an AddRequest message is received by MGW from anMSC Server over the Mc Interface and if the procedure type is PrepareBearer and BNC Characteristics is IP/RTP, MGW responds with an AddReplymessage containing its own IPAddress and PortId.

These and other objects, features and advantages of the presentinvention will become more readily apparent from a reading of thefollowing detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 illustrates the tunneling mechanism.

FIG. 2 illustrates IPBCP data being tunneled though BICC messages usingIPBCTP protocol.

FIG. 3 illustrates existing bearer establishment procedures between twoWCDMA R4 systems using Forward Bearer Delayed Tunneling approach thatprovides for Codec Negotiation between the systems.

FIG. 4 illustrates the proposed optimized bearer establishmentprocedures between two WCDMA R4 systems. IPAddress and Port Numbers arecommunicated using the existing BIWFAddress and BNCId fieldsrespectively, thereby negating the usage of the IPBCTP and IPBCPprotocols. The result is reduced interactions between MSC Servers aswell as between the MSC Server and the Media Gateway thereby providing afaster call setup.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the present invention will now be explainedwith reference to the accompanying drawings. It should be understoodhowever that the disclosed embodiments are merely exemplary of theinvention, which may be embodied in various forms. The followingdescription and drawings are not to be construed as limiting theinvention and numerous specific details are described to provide athorough understanding of the present invention, as the basis for theclaims and as a basis for teaching one skilled in the art how to makeand/or use the invention. However in certain instances, well-known orconventional details are not described in order not to unnecessarilyobscure the present invention in detail.

BICC Bearer Control Tunnelling Protocol (Q.1990) assumes a reliable,sequenced, point-to-point signalling transport service between peerTunnelling PDU Generating and Receiving Entities.

Q.1990 supports the tunnelling of bearer control protocols (BCP) overthe following protocols:

-   -   BICC protocol. BICC tunnelling makes use of BICC APM mechanism,        as defined in Q.765.5 (Signalling system No. 7—Application        transport mechanism: Bearer Independent Call Control) and        Q.1902.4 (Bearer Independent Call Control Protocol—Capability        Set 2—Basic Call Procedures)    -   CBC protocol. CBC tunnelling makes use of the H.248 Tunnelling        package, as defined in Q.1950 (Bearer Independent Call Bearer        Control Protocol).

The operation of the tunnelling mechanism is illustrated in FIG. 1 andthe transport of IPBCP messages is illustrated in FIG. 2.

To overcome the drawbacks of the IP Bearer support that uses IPBCTP andIPBCP, the relevant IP Address and Port Numbers are carried in BICC'sBIWF Address and BNCId protocol fields over the Nc Interface. This helpsin overcoming the need for IPBCTP and IPBCP.

Due to this technique the changes that are required as part of Megaco(H.248.1) and BICC Protocol (Q.1902.4). Procedures for which are asfollows:

-   -   1. BICC Protocol for IP Bearer Support will always need to        perform Prepare Bearer Procedure (Steps 2 and 5 in FIG. 4) in        order to retrieve IPAddress and PortId from its associated MGW.        Currently the originating side performs an Establish Bearer        Procedure (Step 5 in FIG. 3).    -   2. Whenever an AddRequest message is received by MGW (Steps 2        and Steps 5 in FIG. 4) from an MSC Server over the Mc Interface,        if the procedure type is Prepare Bearer and BNC Characteristics        is IP/RTP, MGW should respond with an AddReply message        containing its own IPAddress (in BIWF Address) and PortId (in        BNCId).    -   3. On the originating side, MSC Server sends the remote MGW's IP        Address (in BIWF Address) and PortId (in BNCId) as part of        Remote Descriptor in the AddRequest message (Step 5 in FIG. 4).    -   4. On the terminating side, MSC Server needs to send        ModifyRequest message with Remote Descriptor containing the        originating side's IPAddress (in BIWF Address) and PortId (in        BNCID) (Step 8 in FIG. 4).    -   5. Notify messages (Steps 7 and 8) are not required as IPAddress        and PortId are retrieved from AddReply (Step 6 in FIG. 4)        itself.    -   6. Notify messages (Steps 12 and 13 in FIG. 3) are not required        as IPAddress and PortId are retrieved in AddReply (Step 3 in        FIG. 4).    -   7. APM message (in Step 14 in FIG. 3) is not required since the        IPAddress and PortId has already been conveyed in the previous        APM message (Step 4 in FIG. 4).    -   8. Modify Request (in Steps 15 and 16 in FIG. 3) are not        required since IPAddress and PortId of peer has already been        conveyed as part of AddRequest message (Step 5 in FIG. 4).

From the protocol perspective, when IP Bearer needs to be used, theoptional BIWF Address and BNCId need to be made as mandatory as part ofAPM message.

The above optimization procedure constitutes the invention.

This section continues to outline the procedure proposed and theconcrete benefits that would be arrived at.

FIG. 4 illustrates proposed optimized bearer establishment proceduresbetween two WCDMA R4 systems:

-   -   1. MSC-A initiates bearer establishment procedure by sending        BICC IAM message with BNC Characteristics set to IP/RTP        indicating IP Bearer needs to be established and codec list        indicating that codec negotiation is required.    -   2. MSC-B after processing IAM, performs Prepare Bearer procedure        by sending AddRequest message to MGW-B. AddRequest contains the        selected codec for bearer establishment and BNC Characteristics        set to IP/RTP.    -   3. MGW-B responds with AddReply message that contains the        IPAddress (in BIWF Address) and PortId (in BCNId).    -   4. MSC-B indicates to MSC-A the selected codec for bearer        establishment, BIWF Address and the BNCId through BICC APM        message.    -   5. MSC-A now performs Prepare Bearer procedure by sending        AddRequest message containing the Codec type that needs to be        used for bearer establishment, remote IPAddress and the PortId.    -   6. MGW-A responds with AddReply with its own IPAddress and        PortId.    -   7. MSC-A now responds to MSC-B with MGW-A's IPAddress and PortId        through BICC APM message.    -   8. MSC-B sends a ModifyRequest message to MGW-B containing the        originating sides IPAddress and PortId.    -   9. MGW-B responds with ModifyReply. At this point in time, both        the MGWs are aware of each other's IPAddress and PortId.    -   10. After RabAssignment procedures are successful on MSC-A        towards the source RNC, it sends COT message to MSC-B to        indicate that bearer establishment is successful on the        originating side.    -   11. MSC-B after successful bearer establishment on terminating        side, sends the ACM message to MSC-A.    -   12. And when terminating party answers, MSC-B sends the BICC ANM        message to MSC-A.

The following advantages are secured by following the invented method:

-   -   1. Protocols involved (namely Q.1902.x and H.248.1) are not        changed in terms of addition or removal of parameters, but only        interpretation of existing procedures.    -   2. Support of IP Bearer by a WCDMA R4 system without using        IPBCTP and IPBCP protocols.    -   3. Faster Call Setup due to the minimization and optimal usage        of MGW procedures.    -   4. Processing power saved due to the absence of IPBCP strings        and reduced message interactions. This will result in higher        BHCA in the WCDMA system.    -   5. Reduced message sizes over the Nc (APM Message in BICC        Protocol) and Mc (Add Request and Add Reply Messages in H.248.1)        interfaces thereby providing for an effective utilization of the        signaling resources.    -   6. The Forward Bearer Delayed Tunneling with Codec Negotiation        that is detailed could be extended for Forward Bearer and        Backward Bearer establishment procedures with or without Codec        Negotiation between the two systems achieving the same set of        advantages as detailed above.

It will also be obvious to those skilled in the art that other controlmethods and apparatuses can be derived from the combinations of thevarious methods and apparatuses of the present invention as taught bythe description and the accompanying drawings and these shall also beconsidered within the scope of the present invention. Further,description of such combinations and variations is therefore omittedabove. It should also be noted that the host for storing theapplications include but not limited to a microchip, microprocessor,handheld communication device, computer, rendering device or a multifunction device.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are possible and are apparent to those skilled in the art.Such changes and modifications are to be understood as included withinthe scope of the present invention as defined by the appended claimsunless they depart therefrom.

REFERENCES

-   -   1. ITU-T Recommendation Q.1902.4 (07/2001)—Bearer Independent        Call Control Protocol.    -   2. ITU-T Recommendation Q.1970 (07/2001)—BICC IP Bearer Control        Protocol.    -   3. ITU-T Recommendation Q.1990—BICC Bearer Control Tunneling        Protocol.    -   4. ITU-T Recommendation H.248.1—(05/2002) Gateway Control        Protocol.    -   5. 3GPP TS 29.414 V4.4.0 (2002-03)—Core Networlk Nb Data        Transport and Transport Signaling.    -   6. ITU-T Recommendation Q.765.5—Signalling System No.        7—Application Transport Mechanism: Bearer Independent Call        Control

1-15. (canceled)
 16. A method for Bearer Independent Call Control (BICC)optimization for Internet Protocol (IP) bearer support, comprising thesteps of: initiating by an originating Mobile Switching Center (MSC) abearer establishment procedure by sending a BICC Initial Address Message(IAM) message with a Backbone Network Connection (BNC) characteristicsset to IP/Real-time Transport Protocol (RTP) indicating the need for anIP bearer establishment and a codec list indicating a codec negotiationrequirement.
 17. The method as claimed in claim 16, wherein afterprocessing the IAM, a terminating MSC performs a prepare bearerprocedure by sending an AddRequest message to a terminating mediagateway, and wherein the AddRequest message contains a selected codecfor the IP bearer establishment and the BNC characteristics set toIP/RTP.
 18. The method as claimed in claim 17, wherein a terminatingmedia gateway responds to the AddRequest message with an AddReplymessage that contains an IP address that is included in a BearerInter-Working Function (BIWF) Address and a Port Identification (PortId)that is included in a Backbone Network Connection Identification(BNCId).
 19. The method as claimed in claim 18, wherein the terminatingMSC indicates to an originating MSC the selected codec for the bearerestablishment, the BIWF Address and the BNCId through a BICC ApplicationtransPort Mechanism (APM) message.
 20. The method as claimed in claim19, wherein the originating MSC performs the prepare bearer procedure bysending the AddRequest message containing the codec type that is usedfor the bearer establishment, a remote IP address and the PortId. 21.The method as claimed in claim 20, wherein the originating media gatewayresponds to the AddRequest message with an AddReply message containingits own IP address and PortId.
 22. The method as claimed in claim 21,wherein the originating MSC responds to the terminating MSC with an IPaddress and PortId of an originating media gateway through the BICC APMmessage.
 23. The method as claimed in claim 22, wherein the terminatingMSC sends a ModifyRequest message to the terminating media gatewaycontaining the IP address and PortId of the originating media gateway.24. The method as claimed in claim 23, wherein the terminating mediagateway responds with a ModifyReply message, and wherein each of themedia gateways have received the IP address and PortId of the othermedia gateways.
 25. The method as claimed in claim 24, wherein afterRabAssignment procedures have been successfully performed between theoriginating MSC and a source Radio Network Controller (RNC), theoriginating MSC sends a Continuity (COT) message to the terminating MSCto indicate that the bearer establishment is successful on theoriginating side.
 26. The method as claimed in claim 25, wherein theterminating MSC after successful bearer establishment on the terminatingside, sends an Address Complete message (ACM) to the originating MSC.27. The method as claimed in claim 26, wherein when the terminatingparty answers, the terminating MSC sends a BICC ANswer Message (ANM)message to the originating MSC.
 28. The method as claimed in claim 16,wherein the BICC for IP bearer support performs a prepare bearerprocedure to retrieve an IP Address and Port Identification (PortId)from an associated media gateway.
 29. The method as claimed in claim 16,wherein whenever an AddRequest message is received by a media gatewayfrom a Mobile Switching Center (MSC) Server over an Mc interface, and ifa bearer establishment procedure type is a prepare bearer and the BNCcharacteristics is IP/RTP, the media gateway responds with an AddReplymessage containing its own IP address and Port Identification (PortId).